FPGA : sbRIO-9631, analog input sampling frequency, output to waveform graph

[Kyle81]

Hey all,

     I've been posting for a little bit now. Newb to the arena, etc... I'm still trying to get a grasp... 

Anyways... 

I have a 5Mhz function generator that is generating a sine wave with whatever frequency/duty cyle/offset, etc. I have the signal wire and the ground wired to my sbRIO-9631 board in the ModA/AI0 pin, and the GND right next to it, respectively. I want to show the frequency in anyway possible, in a waveform graph on my host vi. This could be a helluva lot more complex, but when you are first starting, you get excited when you can turn an LED on/off.  Anyways... Let me post my host vi and my fpga vi. I'm running XP pro, labview 8.5.1.

On a side note, Spex... If you read this. You said you have tutorials for the sbRIO-9631, and I found those, but those are for 8.6. Is it possible to dumb those down to 8.5? I'm pretty sure I'd be alot further along if I could see all the examples.. Also, I saw another post where you recommended the embedded systems kit. Possible to get the i/o daughter card, and the eval edition without the sbRIO board? $999 bucks is steep!

Many thanks to anybodys help!

-Kyle

[srm@viewpointusa.com]

zero seems to be a pretty small number of samples to read from the FIFO.

also what is the metronome value for pacing in the FPGA code.

[cirrusio]

Hey Kyle,

What exactly are you asking?  And Stu's right - you probably do want some data and you probably are looking to acquire at some fixed rate.

Matt

[Spex]

I saved most of the tutorial solutions back to LabVIEW 8.5.  I don't have LabVIEW 8.5 on this laptop, so I couldn't validate they made the jump from LabVIEW 2009 to 8.5 without any issues. 🙂

Unfortunately, the daughtercard in the evaluation kit was made specifically for the kit, and I haven't had the chance to document its features and user guide for stand-alone use, so I don't have the ability to sell it on its own.  We assemble the kits in our factory in Hungary, and if the daughtercards are installed improperly, they can damage 1 or both boards. 

The daughtercard doesn't do anything special; it is just a small board with LEDs, switches, and a couple sensors, like a temp sensor, a potentiometer, and a quadrature encoder.  The only difference between using that board with the attached examples vs your own sensors is which pins you connect the sensors to.

If you wanted to move up to a later version of LabVIEW, your campus may have a site license for the latest versions of LabVIEW.  Talk to your software admins.  You can also evaluate LabVIEW 2009 for free with a download, but I wouldn't want you to be stuck at the end of the 30 day trial.

I didn't see any questions in your previous post about the LabVIEW code?  Is it not functioning as you would expect?  What is it doing?

If you want to see an example for how to stream data from FPGA to RT, I would open the LabVIEW example finder and search for the 9205 examples, as the AI circuitry on Single-Board RIO is based on the NI 9205 module for CompactRIO.

Regards,

[Kyle81]

Soo... I guess I was a little vague here.. I tend to have conversations with myself, and forget to clue people in.

Let's say I set my freq generator to 60Hz. Nyquist says over twice the rate. So, twice would be 120 samples/sec. Round it up to 150 samples/sec. Invert that, and get .66667 msec/sample. So... I set the sample rate to that on the FPGA vi.

As far as how much data to read.. Not so sure about that.. It defaulted to zero, but I went up logarithmically, and it didn't change. That leads me to believe though, without knowing the memory threshold. That if the host read from DMA every 2 seconds, then it would have 300 samples to pickup, right? Am I going in the right direction here?

-Kyle

[Spex]

You are going the right direction...  Your math is correct, and requesting 300 samples would time the RT loop at 2 seconds.  The DMA read will wait until the 300 samples are available, or until the timeout is expired before returning. 

What do you mean that when you "went up logarithmically, and it didn't change"?  What didn't change?  Is the graph showing a flat line at 0, or what is wrong?  I would place a probe on the Data output terminal and verify that data is being returned from the DMA.Read function.  If it is, then I would start to investigate your conversion math.  On the FPGA, you are sampling data as a fixed point data type, then coercing it to a U32 (unsigned integer, 0, 1, 2, 3, etc.) for the DMA transfer.  You can set up the DMA transfer for FXP data so that the data you are acquiring on the FPGA is sent to the RT controller intact.  Then on the RT controller you can convert the data to Single or Double precision for visualization on your graph. 

Regards,

[baig]

hey all,

i am a new research student and have just finished the startup and interfacing of the NI sb rio-9631. For certain applications that i intend to work on, i wanted to know of some environmental sensors (humidity, light) that cane be used with this platform. Thanks

Regards

baig

[jareds]

Hi baig,

The sbRIO-9631 has one analog input module that is built onto the board that has 32 voltage input channels.  The channels have a maximum range of +/- 10 V and a minimum range of +/- 200 mV.  It will be able to most sensors that can give a voltage output within those ranges.  It can also read sensors through it's Ethernet port, it's serial port, and it's digital lines.  I'm not sure of specific sensors, but I'm sure if you looked through some you know, you could spot a lot that will work.

Also, you may want to post this on a new discussion.  It will probably get more visibility and thus answers that way.

[baig]

thanx a lot mate.... ur msg was really helpful indeed.... but if u do cme across certain sensors in the meantime, plz let me knw..

thanks

baig

[crist_sosa]

Hi... I would like to know how I have to select the range voltage because in the datasheet of sbrio 9631 I found that the input ranges of voltage are ±10V, ±5V, ±1V, ±0.2V  but I don´t know how to select these voltages.